/*
 *                               POK header
 *
 * The following file is a part of the POK project. Any modification should
 * be made according to the POK licence. You CANNOT use this file or a part
 * of a file for your own project.
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2021 POK team
 */

/* e_asinf.c -- float version of e_asin.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#ifdef POK_NEEDS_LIBMATH
#include "math_private.h"
#include <libm.h>

static const float one = 1.0000000000e+00,        /* 0x3F800000 */
    huge = 1.000e+30, pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
    pio2_lo = 7.5497894159e-08,                   /* 0x33a22168 */
    pio4_hi = 7.8539818525e-01,                   /* 0x3f490fdb */
                                                  /* coefficient for R(x^2) */
    pS0 = 1.6666667163e-01,                       /* 0x3e2aaaab */
    pS1 = -3.2556581497e-01,                      /* 0xbea6b090 */
    pS2 = 2.0121252537e-01,                       /* 0x3e4e0aa8 */
    pS3 = -4.0055535734e-02,                      /* 0xbd241146 */
    pS4 = 7.9153501429e-04,                       /* 0x3a4f7f04 */
    pS5 = 3.4793309169e-05,                       /* 0x3811ef08 */
    qS1 = -2.4033949375e+00,                      /* 0xc019d139 */
    qS2 = 2.0209457874e+00,                       /* 0x4001572d */
    qS3 = -6.8828397989e-01,                      /* 0xbf303361 */
    qS4 = 7.7038154006e-02;                       /* 0x3d9dc62e */

float __ieee754_asinf(float x) {
  float t, w, p, q, c, r, s;
  int32_t hx, ix;

  t = 0;
  GET_FLOAT_WORD(hx, x);
  ix = hx & 0x7fffffff;
  if (ix == 0x3f800000) {
    /* asin(1)=+-pi/2 with inexact */
    return x * pio2_hi + x * pio2_lo;
  } else if (ix > 0x3f800000) { /* |x|>= 1 */
    return (x - x) / (x - x);   /* asin(|x|>1) is NaN */
  } else if (ix < 0x3f000000) { /* |x|<0.5 */
    if (ix < 0x32000000) {      /* if |x| < 2**-27 */
      if (huge + x > one)
        return x; /* return x with inexact if x!=0*/
    } else
      t = x * x;
    p = t * (pS0 + t * (pS1 + t * (pS2 + t * (pS3 + t * (pS4 + t * pS5)))));
    q = one + t * (qS1 + t * (qS2 + t * (qS3 + t * qS4)));
    w = p / q;
    return x + x * w;
  }
  /* 1> |x|>= 0.5 */
  w = one - fabsf(x);
  t = w * (float)0.5;
  p = t * (pS0 + t * (pS1 + t * (pS2 + t * (pS3 + t * (pS4 + t * pS5)))));
  q = one + t * (qS1 + t * (qS2 + t * (qS3 + t * qS4)));
  s = __ieee754_sqrtf(t);
  if (ix >= 0x3F79999A) { /* if |x| > 0.975 */
    w = p / q;
    t = pio2_hi - ((float)2.0 * (s + s * w) - pio2_lo);
  } else {
    int32_t iw;
    w = s;
    GET_FLOAT_WORD(iw, w);
    SET_FLOAT_WORD(w, iw & 0xfffff000);
    c = (t - w * w) / (s + w);
    r = p / q;
    p = (float)2.0 * s * r - (pio2_lo - (float)2.0 * c);
    q = pio4_hi - (float)2.0 * w;
    t = pio4_hi - (p - q);
  }
  if (hx > 0)
    return t;
  else
    return -t;
}
#endif
